Enable svngit2jira integration for Apache Airflow

Details

Description

It seems that as of October 2018 the integration between JIRA and Github has improved and we can now easily have better integration. I think it would be great if we could see commits in the JIRA tickets - for now we cannot see them but it seems rather easy to configure now. All commits in Airflow Github follow the [AIRFLOW-XXXX] JIRA ticket convention in commit description.